Tuning control mechanism for radio receivers



Nov. 9, 1948. w. E. NEWMAN TUNING CONTROL MECHANSM FORRADIO RECEIVERSFiled Deo. 5, 1944 3 Sheets-Sheet l bwl SCHH H TTOR/Vf' Nov. 9, 1948.

w. E. NEWMAN TUNING CONTROL MECHANISM FOR RADIO RECEIVERS Filed Dec. 5,1944 3 Sheets-Sheet 2 W/LL/AM ,4 rrokA/EV Nov. 9, 1948. w. E. NEWMANTUNING CONTROL MECHANISM FOR RADIO RECEIVERS Filed Dc.

5 Sheets-Sheet 3 Patented Nov. 9, 1948 TUNING CONTEROL MECHANISM FORRADIO RECEIVERS William Edward Newman, Chicago, Ill., assigner to RadioCorporation of America, a corporation of Delaware Application December5, 1944, Serial No.'566,666

(Cl. Z50-40) 8 Claims. l

This invention relates in general to tuning control mechanism for Vradioreceivers, and more particularly to control mechanism for effecting in asequential manner the automatic adjustment of the tuning device of aradio receiver to a plurality of transmitted carrier waves having asignal strength above a predetermined minimum.

In control systems of this general type an electric motor is utilized toeffect the tuning, the motor being set into operation by manuallyactuated means and rendered inoperative automatically when the receiverhas been tuned to the carrier wave of a broadcasting station receivedwith sunicient strength.

vIt is one of the objects of the present invention to provide a highdegree of tuning accuracy in a control system of the type mentionedwherein there is utilized a high ratio gearing between the tuningelement and the stationselector means.

A further object of the invention is to provide a combination scanningand hunting type of selector which permits of eiecting in the rstinstance a rough adjustment of the receiver to a station of sullcientsignal strength followed by an accurate adjustment of the receivertuning means.

A still further object of the invention is to provide in combinationwith an adjustable tuning device of a radio receiver tunable through acertain vfrequency range, a reversible electric motor, means operable inresponse to manual control for energizing the motor to actuate thetuning device in a manner such that it is permitted to scan said:frequency range for a signal wave having an amplitude above apredetermined minimum, and

means operable upon reception of such signal carrier wave fordiscontinuing the scanning operation and effecting operation of themotor in a manner such that the tuning device is permitted to hunt forsaid received carrier wave prior to final adjustment ci said tuningdevice to said carrier wave.

A more specic object is to provide a control mechanism for effecting theautomatic adjustment of the tuning device of a radio receiver to atransmitted signal carrier wave having an amplitude above apredetermined minimum, which includes a reversible the tuning device, arotary member movable with the tuning device carrying a pair ofcommutator segments separated by an insulating gap or dead .spot fordetermining the direction of motor o oeration, means for actuating saidmember from ihr' motor, a contact nin cooperatively related with saidrotary member, means -or effecting roelectric motor for actuatingvtation of the segment carrying member and contact pin in unison, meansin response to a signal carrier wave having an amplitude above saidpredetermined minimum for stopping the ccntactpin in a radial positioncorresponding to said carrier wave, and means for effecting closure ofthe motor circuit through the contact pin and one or the other of thecommutator segments to cause continued operation of the motor inthecorresponding direction until'the dead spot between segments contactsthe contact pin at which time the motor will be deenergized to stop thetuning device.

Thenovel features characteristicof my invention are set forth withparticularity in the appended claims. The invention itself, however,both as to its construction and mode of operation together with `furtherobjects and advantages thereof, Will best be understood by reference tothe following description taken in connection with the -accompanyingdrawings, in which:

Fig. 1 is a view, partly in section, disclosing schematically thecontrol mechanism according to one form of the invention;

Fig. 2 is a cross-sectional view taken on the line 2 2 of Fig. 1;

Fig. 3 is a partial view of Fig. 1 showing the condition of theapparatus when operating as a scanning type of tuner; y

Fig. 4 is a view similar to Fig. 3 showing the condition of theapparatus when operating as a hunting type of tuner;

Fig. 5 is a modied form of Vthe invention; and

Fig. 6 is an end View of Fig. 5.

In accordance with the invention, the station selector means of thecontrol mechanism consists of a motor-actuated two-segment commutatorseparated by a dead spot or insulating gap which upon arriving incontact with a single contact, adjustably positioned in reference to thestation carrier to be received, `stops the hunting operation of themotor. The motor is of the reversible type having its field windingsconnected to the two segments of the commutator in the conventionalmanner. The selector Contact and commutator both rotate together whenthe selector is scanning or running from one station to the next, butwhen a station carrier is found by the tuning element the selectorcontact is locked in position. .and the coiimutator and tuning elementcontinue in their original direction of rotation due to inertia.Eventually they stop and then reverse their direction of rotation due tothe motor torque being reversed. The moment the signal carrier is foundby the tuning element, the selector contact locks itself to a fixed partof the mechanism and becomes a marker or reference point to which theselector finally cornes to rest. The contact is carried by a rotatablearm of low mass so that it has practically no overtravel and willtherefore stop almost instantly whereas the tuning element and thecommutan tor have in comparison a much greater mass.

Briefly, the device functions as a scanning type of selector` whenrunning from one station to the next, having a motor reversing means ateach limit of the tuning stroke, and is automatically converted to ahunting type of selector when the tuning element arrives at a stationcarrier of sufficient strength. With the use of this principle only onecontact point is required for stopping at any angular position, sincethe contact point and the commutator rotate together until the two areseparated by the incoming signal. It is possible, therefore, to obtainextreme accuracy in the stopping positions of the tuning element bygearing down so that the selector makes thousands of revolutions to onerevolution of the tuning element.

Referring now to the drawings, and more particularly to Figs. l and 2,there is shown at IU the tuning device of a radio receiver representedas a conventional type of rotary variable condenser, suitably supportedfrom a bracket II mounted on a support I2 which may be the receiverchassis. On the shaft I3 of the rotary element of the tuning device ismounted a worm wheel I4 which meshes with a worm I5 formed at one end ofa motor-driven shaft i5. The shaft is `iournalled in a bearing I1carried by a bracket IS also affixed to the receiver chassis I2. Affixedto the shaft I6 is a friction wheel I9 which is adapted to be driven bya second friction wheel 2f! mounted on a shaft 2i of an electric motorindicated generally at 22.

The motor is of the reversible type being provided with an armature 23to which the driving shaft 2| is attached and with a pair of fieldwindings 2li and 25. Thearmature is capable of slight axial movement,being constrained, by spring means not shown, to assume the nondrivingposition shown in Fig. l.. Upon the motor becoming energized, thearmature is thrust outwardly in an axial direction in opposition to thespring means to effect the coupling or driving relation between the`driving wheel 20 and the driven wheel I9,

The common terminal of the motor field windings 24 and 25 is connectedby way of a conductor 25 to one side of a source of power 21 which isconstituted by a step-down transformer for stepping down the 110 voltsavailable at the house current power supply mains to about 24 voltsnecessary for operating the motor, The other side of the power source(transformer secondary) is connected through a conductor 23 to a movablecontact 29 of a switch 3B, to be described later. The opposite terminalsof windings 2d and 25 are connected, respectively, by way of conductors3I and 32 to fixed contacts 33 and 34 of a motor reversing switch 35.The moveable element of this switch is in the form of a blade 36 whichis centrally pivoted at 31 and is provided with an operating lever 38disposed in the path of travel of a pair of pins 39 and Ali affixed tothe side of worm wheel Sli. The pins are spaced apart 180 to correspondwith the two limiting positions of the tuning device.

In the position shown in Iiig` l the tuning de vice has just reached oneof its limits (the minimum capacity position) whereat switch blade 36 issnapped into the position shown, by action of pin against lever 3S. rhiscloses the motor circuit through the field winding 25 which causes themotor to operate in the reverse direction, that is in the directionopposite to that which moved the tuning device to the minimum capacityposition. The motor will so operate until the tuning condenser is movedto its other limit (the maximum capacity position) whereat switch blade35 is snapped into its other position by action of pin iii against lever33. This closes the rnotor circuit through the other eld winding 2liwhich causes the motor to again reverse its direction of operation. rEheback-and-forth movement of the tuning device between minimum and maximumcapacity positions brought about by the motor when under control of thereversing switch 35 will here-- inafter be referred to as the scanningoperation.

Afiixed to the motor-driven tuning shaft I6 at the right is a drummember il provided with a flange 42 to which there is attached a plate43. Carried by this plate is a strip of insulation 44 to which there isattached a pair of conimutator segments 'l5 and 46 separated by a narrowgap or dead spot 4i. An insulating sleeve 43 is provided on the outersurface of the drum and carried on the sleeve are a plurality ofcollector rings 49, 5e, 5i and '52. Rings 49 and 5u are electricallyconnected, respectively, to commutator segments and it, and rings 5I and52 are electrically connected to the opposite terminals of a solenoid 53contained within and adapted to rotate with the drum 4 I. Each ring hasassociated with it a contact brush, these being shown respectively at54, 55, 5t and 5l, suitably supported on an insulating block 53 carriedon a bracket 59. Contact brushes 5&1 and 55 are connected respectivelyto the uncommon terminals of the motor field windings 25 and 24 by wayof conductors B0 and 60', and contact brushes 56 and 5'! have connectedto them1 respectively, a conductor iii which leads to the -B terminal,and a conductor 62 which leads to the +B terminal of the receiver powersupply through a solenoid-controlled armature, later to be described.

A bracket 63 mounted on the receiver chassis I2 has its upper part 63'offset slightly toward plate 4S to present a surface in parallelrelation therewith. Formed integral with bracket part 53 or otherwiseattached thereto is a bushing 64 which serves as a bearing for anaxially shiftable and rotatable shaft 55, disposed in axial relationwith reference to shaft I5. The left end of shaft 65 carries a'plunger56 which in the deenergized state of solenoid 4I extends partly into thedrum in the manner shown in Fig. 1. The shaft 65 also carries to theright of the plunger a contact arm @l which is provided on its oppositefaces, in concentric relation with the plunger, with annular layers 68and 59 of friction material, such as rubber. In the position shown forcontact arm 51 the friction layer 5S is in contact relation with theside of bracket part 53' facing it, shaft 55 and contact arm 61 beingurged to that position by means of an expansion spring 'Iii `disposedbetween a pair of washers 'II and 12. The latter is keyed to move` withthe shaft while the former always remains in xed position in contactwith the end of bushing 561. With shaft 65 and arm G'l axially shiftedto the left, due to energization of solenoid 4I, the friction layer 68on the opposite side of the arm is forced into Contact relation with therotary drum plate 43. rAsfa-consequencecontactarm161 is causedto=berotated along with vdrum 4|.

Contact arm I6"! lhas affixed to it an insulating member 73 which`carries 'a contact pin 14. In order that contactimaybe had between thepin and thecommutator --41 at all times regardless of Vthe 'axialposition `of the contact arm, the shank 15 of the pin .isslidablymounted with a bushing lfcarried byzmember 13 and a coil spring 1111s`disposed between the iiange of the bushing and the 4`pin head 4'|8.

`A...ilexible 'conductor '|9 vis connected between the contactxpinpandgacollector ring insulatingly mounted on the bushing .64. A brush contactf8| suitably `supported on an insulating bracket 82land arranged tocontact with vring 8U is-connected by way of 4'a conductor '83.and aresistor 84 to aflxed contact 185 yof `the switch 30. A second fixedcontact86 lof the switch 30 is connected by way of a `conductor 81 tothe center contact 88 of motorreversing switch 35 which is electricallyconnected to the pivoted switch blade 36. Switch 301s' supported fromthe :chassis |-2 'by abracket 99.1andzis so positioned ythat its centerflexible contact 29 is disposed adjacent to land in the path of an.insulating member 90 carried at the end of Ashaft .65, .the position ofswitch contact 29 being .determined by the .axial position of the shaft65.

At 9| is shown a control tube which may constitute one of the radiofrequency or intermediate frequency stages of the radio receiver to becontrolled or a separate tube which is arranged to have impressed on itsinput electrodes a portion of the received signalenergy. A solenoid `92is connected in the plate circuit of tube 9|, that is, between the`plate electrode of the tube and the +fB terminal of the receiver powersupply. The armature 93 iis alsoconnected to the -l-'Blterminal and isarranged by spring means 94 -to assume the inormal vposition shown, thatis, away 'from a'xed contact 95 to which `conductor f62 is connected.For initiating operation `of thecontrol mechanism, `there is connectedbetween-the plate side of LAthe'solenoid Z92 and the -`B terminal -orground a Ymanual station Vselector switch'orpushbutton 96.

The control mechanism above described operates =in the -followingmanner: 'For `-tuning in a station all that'need be done by the operatoris to actuate pus`h-button 96. This completes .-a circuit through`solenoid 92 as follows: from -l-B, solenoid92, closed switch 1`96, to-B or ground. As a result armature '93 `will vbe pulled Jover to contactI95 -in lopposition to spring 9'4 to close a the :position yof blade`36of motor reversing 'switch 35. This condition of 4themechanisni :for:carrying out the scanning operation is shown :diagrammatically in Fig.3, the motor actuating the tuner I0 between Iits .two limiting positionsinorder to scan the frequency range ;0f the `receiver. During the:scanning oper-ation :com-

mutator-M-M and-contactpin .1.4 will .rotatein unison but `.due to theaxial .movement `of :shaft 65 vcontacts 29 and 85 which providecontinuity from the contact pin to `the motor vare broken.v The motorhaving started rotating, the station selector button 96 may be releasedbut thesolenoid remains energized due to the .flow of "current intheplate circuit of control ytube 9| and will continue to .be energized Haslong as the tuner is 4not tuned to a carrier wave of requisite signalstrength.

When, however, the tuner is actuated to aposition where the receiver istuned to a station carrier of predetermined strength the plate currentthrough control tube 9| willbevreduced suiciently to cause release ofplunger -66 and, :incidentally, contact arm 6'| which, due to action ofspring `1|) is forced against the face of bracket part 63', armremaining fixed in .a radial vdirection as determined by the point ofrelease.

l The commutator 45-41, however, continues'in its original direction ofArotation due to inertia. Switch contacts 29 and S5 are now closed byreason of `the return of 'shaft 65 .to the right, sothat contact pin '|4on one .or the other of commutator segments 45, 46 provides continuityforlthe'motor circuit. This condition .of the mechanism for carrying outthe "hunting operation is shown diagrammatically in Fig. 4, the motordriving the commutator back and .forth until .its gap 41 coincides withcontact pin 14 -when the motor circuit is broken, deenergizing `themotor and causing the .tuner l0 to stop at the tuned-in position atwhich the receiver is adjusted to the carrier wave having a signalstrength of predetermined value.

During the hunting operation the commutator gap passes the vcontact pinseveral times, the commutator coming to rest when the energy due toinertia is used up. In order to reduce the motor speed and therefore thenumber of back and forth movements of vthe commutator during the huntingoperation, the resistor 84 is connected in series with the motorcircuit. The motor-reversing switch .35, it will be noted, is notincluded in the motor ycircuit when the commutator is hunting sinceswitch 3B isfopen at its contacts y29, 86;

After a station is tuned-in in the manner described, the next station insequence of requisite signal strength can be tuned-inby-actuating thestation selector button anew.

It Awill be seen .therefore from the description given above that byreason of the instantaneous setting of the low mass -contact arm inresponse to a predetermined signal and 'by reason also 'of the highratio gear reduction between the commutator and .the tuning elementthere is secured a .high degree-of tuning accuracy.

A modified form of the invention is disclosed in Figs. and-Gfin whichthepositions of the contact pin "I4 andthe commutatorAE-H aretransposed,the .same yreference characters as Vemployed in Figs. l land 2 beingused to designate the same'or equivalent elements. vExcept for the fact`that the commutator is shifted in an axial direction upon energization'of the solenoid 53 tofbe locked for rotation with drum i during thescanning operation, and that contact -pin 'M is .oscillated back andforth with respect to the commutator segments during the huntingoperation, the vcontrol mechanism shown. in Figs. 5 and 6 operates inexactly the same manner as that disclosed in Figs, l and 2. A yfurtherdescription thereof is therefore believed unnecessary.

While I have shown and :described preferred embodiments of theinvention, it will be `under-- 7 stood by those skilled in the art thatmodications and changes may be made without departing from the spiritand scope of the invention.

What claim is:

1. The combination in a radio receiver, oi an adjustable tuning devicetunable through a certain frequency range, a reversible electric motorfor actuating the tuning device, first control means including asolenoid and a two-position switch which is under the control of thearmature of said solenoid, said control means being operable inresponse'to manual control for energizing the solenoid and, through saidswitch in one of its positions, also the motor to actuate the tuningdevice in a manner such that it scans said frequency range in search fora carrier wave of a signal strength above a predetermined minimum, andsecond control means operable upon reception of such signal carrier Waveadapted to deenergize said solenoid thereby to move the switch to itsother position for deenergizing the motor and discontinuing the.scanning operation, and circuit means closed through the switch in saidother position for eifecting operation of the motor in a manner suchthat the tuning device hunts for said received carrier wave prior tofinal adjustment thereof to said carrier wave.

2. The combination in a radio receiver, of an adjustable tuning devicetunable through a certain frequency range, a reversible electric motorfor actuating the tuning device having associated with it alternativeenergizing circuits, first control means including a solenoid and atwo-position switch which is under the control of the armature oi saidsolenoid, said control being operable in response to manual control forenergizing the solenoid and, through said switch in one of itspositions, also the motor through one of its circuits to actuate thetuning device in a continuous manner such that it scans said frequencyrange for a carrier wave of a signal strength above a predeterminedminimum, and second control means operable upon reception of such signalcarrier wave adapted to deenergize said solenoid thereby to move theswitch to its other position for deenergizing said one motor circuit tothereby discontinue the scanning operation, and circuit means closedthrough the switch in said other position for effecting operation of themotor through its other circuit in a manner such that the tuning devicehunts for said received carrier wave prior to final adjustment thereofto said carrier wave.

3. Control mechanism for effecting the automatic adjustment of thetuning device of a radio receiver to a transmitted signal carrier wavehaving an amplitude above a predetermined minimum, comprising areversible electric motor for actuating the tuning device, a rotarymember movable with the tuning device carrying a pair of commutatorsegments separated by a dead spot for determining the direction of motoroperation, means for actuating said member from the motor, a contact pincooperatively related with said rotary member, means for effectingrotation of the segment carrying member and contact pin in unison, meansin response to a signal carrier Wave having an amplitude above saidpredetermined minimum for stopping the contact pin in a radial position.corresponding to said carrier wave, and means for eiiecting closure ofthe motor circuit through the contact pin and one or the other of thecommutator segments to cause continued operation of the motor in thecorresponding direction until the dead spot between segments contactsthe contact pin at which time the motor will be deenergized to stop thetuning device.

4. Control mechanism for efecting the automatic adjustment of a radioreceiver tuning device to a transmitted signal carrier wave having anamplitude above ,a predetermined minimum, comprising a reversibleelectric motor, a commutator provided with a pair of conducting segmentsspaced apart by an insulating strip, means operable during operation ofthe motor for actuating the tuning device and the commutator, a rotarycontact pin arranged in cooperative relation with the commutator, acontrol member adapted upon actuation to initiate operation of themechanism, means operable in response to actuation of the control memberfor effecting rotation of the commutator and contact pin in unison, andmeans operable in response to a signal carrier wave having an amplitudeabove said predetermined minimum for making the last-mentioned operablemeans ineffective, whereby the contact pin is stopped in a radialposition corresponding to said carrier wave, the contact pin in itsstopped position remaining in contact with one or the other of thecommutator segments to thereby determine the direction oi motoroperation which continues until the insulating strip of the commutatorarrives in contact with the contact pin to deenergize the motor andcause the tuning device to stop at thc position which tunes the receiverto said carrier wave.

5. Control mechanism as defined in claim 4 wherein the means operableduring operation of the motor effects actuation of the tuning device andcommutator in unison, the latter at a greater speed than the former.

6. Control mechanism as dened in claim 4 wherein the actuating means forthe commutator includes a direct drive from the motor and that for thetuning device includes reduction gearing.

7. Control mechanism for effecting automatic adjustment of the tuningdevice of a radio receiver to a transmitted signal carrier wave havingan amplitude above a predetermined minimum, comprising a reversibleelectric motor for driving the tuning device, a pair of alternativecircuits for energizing the motor, a, rotary member movable with thetuning hdevice in a predetermined relation carrying a pair of commutatorsegments separated by a dead spot, an axially shiftable shaft, a rotaryarm aiTiXed to said shaft and carrying a Contact pin, a twopositionswitch controlled by said shiftable shaft adapted in one position toenergize the motor through one of said alternative circuits and in theother position to energize the motor through the other motor circuitwhich includes the commutator segments and contact pin, a control memberupon actuation adapted to initiate operation of the mechanism byenergizing said one motor circuit, means operable in response toactuation of the control member for effecting rotation of the commutatorand contact pin in' unison, and means operable in response to a signalcarrier wave having an amplitude above said predetermined minimum formaking the ylastmentioned operable means ineective whereby the contactpin is prevented from rotating with the commutator and is stopped at aradial position corresponding to said carrier wave, said contact arm insaid stopped position cooperating with one or the other of thecommutator segments to cause continued operation of the motor in thecorresponding direction until the dead spot between segments is moved incontact with the contact pin at which time the motor is deenergized tostop the tuning device at the point of adjustment Whereat the radioreceiver is tuned to said signal carrier Wave.

8. Mechanism for eiecting automatic adjustment of a radio receivertuning device to a transmitted signal carrier Wave having an amplitudeabove a predetermined minimum, comprising a reversible electric motor,means including reduction gearing for actuating the tuning device fromthe motor, a rotary member carrying a pair of commutator segments fordetermining the direction of motor operation, a fixed member spaced fromthe rotary member, means including a direct drive for actuating saidrotary member from the motor, a rotary contact arm adapted for axialmovement between said rotary and fixed members, a contact pin carried bysaid arm and arranged to cooperate with said commutator segments, asolenoid upon being energized arranged to shift the contact arm indriving rela tion with the rotary member, a normally open switchincluded in the motor circuit actuated to closed position with theshifting of the Contact arm, means for energizing the solenoid in theabsence of a signal carrier Wave having an amplitude above saidpredetermined minimum and for deenergizing the solenoid upon receptionof such carrier wave, manual means for initiating operation of themechanism, means in response to a signal carrier wave having anamplitude above said minimum for deenergizing the solenoid to therebyrelease the contact carrying arm which assumes a fixed position in aradial direclll REFERENCES CITED The following references are of recordin the file of this patent:

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